Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
  • C08G65/02—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from cyclic ethers by opening of the heterocyclic ring
  • C08G65/32—Polymers modified by chemical after-treatment
  • C08G65/329—Polymers modified by chemical after-treatment with organic compounds
  • C08G65/331—Polymers modified by chemical after-treatment with organic compounds containing oxygen
  • C08G65/332—Polymers modified by chemical after-treatment with organic compounds containing oxygen containing carboxyl groups, or halides, or esters thereof
  • C08G65/3322—Polymers modified by chemical after-treatment with organic compounds containing oxygen containing carboxyl groups, or halides, or esters thereof acyclic
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
  • A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
  • A61L15/42—Use of materials characterised by their function or physical properties
  • A61L15/60—Liquid-swellable gel-forming materials, e.g. super-absorbents
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/08—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides with the hydroxy or O-metal group of organic compounds

Definitions

• the present invention relates to a simplified process for the esterification of unsaturated acids with polyalcohols and use of the reaction mixtures obtainable in this way.
• SAP superabsorbent polymers
• SAP superabsorbent polymers
• These are networks of flexible hydrophilic polymers, which may be both ionic and nonionic in nature. These are capable of absorbing and binding aqueous fluids to form a hydrogel, and are therefore preferred for the manufacture of tampons, diapers, sanitary napkins, incontinence articles, children's exercise underwear, shoe inserts, and other hygiene articles used in the absorption of body fluids.
• Superabsorbents are also used in other fields of technology in which liquids, in particular water or aqueous solutions are absorbed.
• These areas are eg storage, packaging, transport (packaging material of water-sensitive articles, such as flower transport, shock protection); Food sector (transport of fish, fresh meat, absorption of water, blood in fresh fish / meat packaging); Medicine (wound plaster, water-absorbing material for burn dressings or for other weeping wounds), cosmetics (carrier material for pharmaceutical chemicals and medicaments, rheumatism plaster, ultrasound gel, cooling gel, cosmetic thickener, sunscreen); Thickener for oil / water or water / oil emulsions; Textile (gloves, sportswear, moisture regulation in textiles, shoe inserts); chemical process industry.
• transport packaging material of water-sensitive articles, such as flower transport, shock protection
• Food sector transport of fish, fresh meat, absorption of water, blood in fresh fish / meat packaging
• Medicine wound plaster, water-absorbing material for burn dressings or for other weeping wounds
• cosmetics carrier material for pharmaceutical chemicals and medicaments, rheumatism plaster, ultrasound gel, cooling gel, cosmetic thickener, sunscreen
• the superabsorbent are usually in the so-called.
• Absorbent core which includes other materials such as fibers (cellulose fibers), which buffer as a kind of liquid reservoir, the spontaneously charged amounts of liquid and a good sewerage of body fluids in the absorbent core towards the superabsorbent to ensure.
• the polymer Due to the higher loading of the hygiene article (polymer per unit area), the polymer must not form a barrier layer for the subsequent liquid in the swollen state. If the product has good transport properties, optimum utilization of the entire hygiene article can be guaranteed. The phenomenon of gel blocking is thus prevented, which leads in extreme cases to the escape of the liquid, the so-called leakage of the hygiene article. Fluid transfer and distribution is therefore crucial in the initial absorption of body fluids.
• Hydrogels which have a high gel strength in the swollen state have good transport properties. Gels with only low gel strength are deformable under an applied pressure (body pressure), clog pores in the superabsorbent / cellulose fiber absorbent and thereby prevent further fluid absorption. An increased gel strength is usually achieved by a higher cross-linking, whereby, however, the retention of the product is reduced.
• An elegant method for increasing the gel strength is the surface postcrosslinking. In this process, dried superabsorbers with average crosslinking density are subjected to additional crosslinking. Surface postcrosslinking increases the crosslink density in the shell of the superabsorbent particles, raising the absorption under pressure to a higher level.
• the core of the superabsorbent particles has an improved absorption capacity compared to the shell due to the presence of mobile polymer chains, so that the shell construction ensures improved fluid transfer without the gel blocking effect occurring. It is quite desirable that the total capacity of the superabsorbent is not exploited spontaneously but with a time delay. Since the hygiene product is usually applied several times with urine, the absorption capacity of the superabsorbent has reasonably not be exhausted after the first disposition.
• Hydrophilic, highly swellable hydrogels are in particular polymers of (co) polymerized hydrophilic monomers, graft (co) polymers of one or more hydrophilic monomers on a suitable graft base, crosslinked cellulose or starch ethers, crosslinked carboxymethylcellulose, partially crosslinked polyalkylene oxide or natural products swellable in aqueous liquids, such as guar derivatives.
• Such hydrogels are used as aqueous solution-absorbing products for making diapers, tampons, sanitary napkins and other sanitary articles, but also as water-retaining agents in agricultural horticulture.
• hydrophilic, highly swellable hydrogels are generally surface or gel postcrosslinked. This postcrosslinking is known per se to the person skilled in the art and is preferably carried out in aqueous gel phase or as surface postcrosslinking of the ground and screened polymer particles.
• (meth) acrylates of alkoxylated polyvalent C 2 -C 10 -hydrocarbons are known as crosslinkers. These can be used as mixtures with by-products from the manufacturing process.
• a disadvantage of these compounds is that for at least partial separation of starting materials and by-products - the crosslinkers used in the mentioned document have a content of acrylic acid of less than 0.1% by weight - complex purification operations are required.
• a disadvantage of this process is that the reaction times are up to 35 hours due to the low reaction temperature and the excess acid in the reaction mixture is removed by neutralization with subsequent phase separation.
• WO 2001/14438 (Derwent abstract no. 2001-191644 / 19) and WO 2001/10920 (Chemical Abstracts 134: 163502) describe processes for the esterification of (meth) acrylic acid with Polyalkylenglykolmonoalkylethern in the ratio 3: 1-50: 1 in the presence of acids and polymerization inhibitors and, after deactivation of the acidic catalyst, copolymerization of the residue from (meth) acrylic acid ester and (Meth) acrylic acid at pH 1.5-3.5, and its use as a cement additive.
• a disadvantage of this method is that it is limited to Polyalkylenglykolmonoalkylether that the catalyst must be deactivated and that such copolymers can not be used as crosslinkers for hydrogels, since they have only one functionality.
• the object was to simplify the production process for substances that can be used as radical crosslinkers for superabsorbents.
• the molar excess of B to A is (depending on the hydroxy group to be esterified in the polyhydric alcohol A) at least 1.05: 1, preferably at least 1.1: 1, more preferably at least 1.25: 1, most preferably at least 1.5: 1 and in particular at least 2.5: 1.
• B is in an excess of, for example, greater than 5: 1, preferably greater than 10: 1, more preferably greater than 20: 1, even more preferably greater than 50: 1, in particular greater than 75: 1 and especially greater than 100 : 1 inserted.
• esterification products thus obtainable can be used as radical crosslinkers in hydrogels essentially without further purification, especially without substantial separation of the excess of carboxylic acid B and the content of esterification catalyst C.
• Crosslinking in this document is understood as meaning radical crosslinking (gel crosslinking, internal crosslinking, cross-linking of linear or slightly crosslinked polymer) unless otherwise stated.
• This crosslinking can take place via free-radical or cationic polymerization mechanisms or other, for example Michael addition, esterification or transesterification mechanisms, preferably by free radical polymerization.
• Hydrogel-forming polymers which absorb aqueous liquids are preferably those having an absorption of distilled water of at least their own weight, preferably 10 times their own weight, and this absorption is preferably also achieved under a pressure of 0.7 psi.
• Polyalcohols A which can be used according to the invention are compounds which have at least two hydroxyl functions (-OH), preferably at least three, particularly preferably three to ten, very particularly preferably three to six and in particular three to four.
• the polyalcohols may be aliphatic, cycloaliphatic or aromatic, preferably aliphatic or cycloaliphatic and very particularly preferably aliphatic, straight-chain or branched and optionally substituted with functional groups.
• the polyalcohols have from 2 to 50 carbon atoms, and preferably from 3 to 40.
• the molecular weight of the polyhydric alcohols used is generally below 5000 g / mol, preferably below 2500 g / mol, more preferably below 1500 g / mol, very preferably below 1000 g / mol and in particular below 800 g / mol.
• Preferred polyalcohols A are polyols, functionalized polyols, alkoxylated polyols, sugar alcohols, partially alkoxylated sugar alcohols, polyetherols, polyesterols, at least partially alkoxylated polyesterols and at least partially saponified, alkoxylated polyesterols.
• polyols examples include trimethylolbutane, trimethylolpropane, trimethylolethane, neopentyl glycol, neopentyl glycol hydroxypivalate, pentaerythritol, glycerol, 1,2-ethylene glycol, 1,2-propylene glycol, 2-ethyl-1,3-propanediol, 2-methyl-1,3-propanediol, Hydroquinone, bisphenol A, bisphenol F, bisphenol B, 2,2-bis (4-hydroxycyclohexyl) propane, 1,1-, 1,2-, 1,3- and 1,4-cyclohexanedimethanol, 1,2-, 1 , 3- or 1,4-cyclohexanediol, but-2-ene-1,4-diol and but-2-yne-1,4-diol.
• the polyols can also carry additional functionalities such as ether functions (-O-), carboxyl functions (-COOH) or C 1 -C 4 -alkyloxycarbonyl (ester groups), where C 1 -C 4 alkyl in this specification methyl, ethyl, iso Propyl, n-propyl, n-butyl, iso -butyl, sec -butyl or tert -butyl.
• ether functions -O-
• carboxyl functions -COOH
• C 1 -C 4 -alkyloxycarbonyl ester groups
• polystyrene resin examples include ditrimethylolpropane, dipentaerythritol, dimethylolpropionic acid, dimethylolbutyric acid, trimethylolacetic acid, hydroxypivalic acid and the 2-hydroxyethyl or C 1 -C 4 -alkyl esters of these acids.
• Preferred polyols are those of the formula (I):
• the alkyl radicals may each be straight-chain or branched.
• R 1 and R 2 are hydrogen, methyl, ethyl, iso -propyl, n-propyl, n-butyl, iso -butyl, sec- butyl, tert- butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-decyl, hydroxymethyl, carboxyl, methoxycarbonyl, ethoxycarbonyl or n-butoxycarbonyl, preferably hydrogen, hydroxymethyl, methyl and ethyl, more preferably hydroxymethyl, methyl and ethyl.
• polyhydric alcohols of the formula (I) are trimethylolbutane, trimethylolpropane, trimethylolethane, neopentyl glycol, pentaerythritol, 2-ethyl-1,3-propanediol, 2-methyl-1,3-propanediol, 1,3-propanediol, dimethylolpropionic acid, dimethylolpropionic acid methyl ester, Dimethylolpropionic acid ethyl ester, dimethylolbutyric acid, dimethylolbutyric acid methyl ester or dimethylolbutyric acid ethyl ester, preference is given to neopentyl glycol, trimethylolpropane, pentaerythritol and dimethylolpropionic acid, very particular preference to neopentyl glycol, trimethylolpropane and pentaerythritol and in particular trimethylol
• sugar alcohols examples include sorbitol, mannitol, maltitol, isomalt, diglycerol, threitol, erythritol, adonite (ribite), arabitol (lyxite), xylitol and dulcitol (galactitol).
• polyetherols are poly-THF having a molecular weight between 162 and 2000, preferably between 162 and 1458, more preferably between 162 and 1098, very particularly preferably between 162 and 738 and in particular between 162 and 378, poly-1,3-propanediol and Poly-1,2-propanediol having a molecular weight between 134 and 1178, preferably between 134 and 888, more preferably between 134 and 598 and most preferably between 134 and 308, polyethylene glycol having a molecular weight between 106 and 898, preferably between 106 and 458 , more preferably from 106 to 400, most preferably between 106 and 235 and especially diethylene glycol, triethylene glycol and tetraethylene glycol.
• polyesterols are e.g. those into consideration, such as can be prepared by esterification of polycarboxylic acids, preferably dicarboxylic acids, with the abovementioned polyols.
• polyesterols are known to the person skilled in the art.
• Preferred polycarboxylic acids include oxalic acid, maleic acid, fumaric acid, succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedioic acid, o-phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, azelaic acid, 1,4-cyclohexanedicarboxylic acid or tetrahydrophthalic acid, their isomers and hydrogenation products and also esterifiable derivatives such as anhydrides or dialkyl esters, for example C 1 -C 4 -alkyl esters, preferably methyl, ethyl or n-butyl esters, of the acids mentioned are used.
• hydroxyl-bearing carboxylic acids or lactones are 4-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, pivalolactone or ⁇ -caprolactone into consideration.
• Suitable polyols are the abovementioned polyfunctional alcohols, preferably neopentyl glycol, Trimethylolpropane, trimethylolethane, pentaerythritol, dimethylolpropionic acid or dimethylol butyric acid into consideration.
• Examples of Y are a single bond, methylene, 1,2-ethylene, 1,3-propylene, 1,4-butylene, 1,6-hexylene, 1,7-heptylene, 1,8-octylene, cis-1,2 -Ethenylene, trans-1,2-ethenylene, 1,2-, 1,3- or 1,4-phenylene, 1,2-cyclohex-1-enylene, 1,2-, 1,3- or 1,4 Cyclohexylene, 4-carboxy-1,2-phenylene, 2-carboxy-1,4-phenylene or 1-carboxy-2,4-phenylene.
• Preferred groups Y are 1,2-ethylene, 1,4-butylene and 1,2-, 1,3- or 1,4-phenylene.
• reaction mixtures of at least partially saponified polyesterols are used as polyalcohols A for the preparation of the ester F.
• the e.g. polyesterols described above with a suitable base at least partially saponified and then, optionally after separation of remaining in the reaction mixture basic constituents, esterified with the carboxylic acid B.
• Suitable bases are, for example, NaOH, KOH, Ca (OH) 2 , lime milk, Na 2 CO 3 or K 2 CO 3 , for example as a solid, solution or suspension, preferably in the form of a 10-50% by weight solution, more preferably in the form a 20-40% by weight aqueous solution.
• the saponification i. the cleavage of the ester groups contained in the polyesterol, for example, at least 10% based on the ester groups in the starting compound, preferably at least 25%, more preferably at least 50%, most preferably at least 75% and in particular at least 90%.
• the basic ingredients e.g. the basic salt of the carboxylic acid to be removed from the reaction mixture may be, for example, via ion exchangers, e.g. Acid or strong acid ion exchangers take place.
• reaction mixture is then acidified and esterified with the carboxylic acid B as described.
• Polyester (meth) acrylates can be used in several stages or in one stage, such as in EP-A 279 303 described, be prepared from (meth) acrylic acid, polycarboxylic acid and polyol.
• alkoxylated polyols and polyester olev which are obtainable by reacting a polyol or polyesterol with at least one alkylene oxide.
• the underlying alcohol to be esterified has the formula VIIa, R 8 - (O (CH (R 10 ) CH (R 10 ) O) y H) x (VIIa), wherein R 8 , R 10 , x and y are as defined above.
• the compounds of formula (VII) are generally from 2 to 10 carbon polyhydric alcohols VIIa which are alkoxylated with between 2 and 8 alkylene oxide units per hydroxy group and whose terminal hydroxy group of each alkylene oxide chain is esterified with a 2 to 10 carbon unsaturated carboxylic acid or esters thereof is.
• the starting alcohol is preferably a polyhydric alcohol having 3 to 6 carbon atoms, which preferably carries 2 to 4 hydroxyl groups.
• the starting alcohol is particularly preferably trimethylolpropane, glycerol, pentaerythritol, 1,3-propanediol, propylene glycol, 1,4-butanediol or butylene glycol. Very particular preference is given to trimethylolpropane, glycerol and pentaerythritol as starting alcohol.
• Suitable alkylene oxides are, for example, ethylene oxide, propylene oxide, isobutylene oxide, vinyl oxirane and / or styrene oxide.
• the alkylene oxide chain may preferably be composed of ethylene oxide, propylene oxide and / or butylene oxide units. Such a chain may be composed of a species of an alkylene oxide or a mixture of alkylene oxides. When a mixture is used, the different alkylene oxide units may be random or block or blocks of individual species.
• Preferred as the alkylene oxide is ethylene oxide, propylene oxide or a mixture thereof, more preferably it is ethylene oxide or propylene oxide and most preferably ethylene oxide.
• one radical R 10 per alkylene oxide unit is preferably hydrogen and the other is methyl or hydrogen, particularly preferably both radicals R 10 are hydrogen.
• the preferred number of alkylene oxide units in each chain depends on the number of chains.
• the esterifying agent is a straight chain or branched chain ethylenically unsaturated carboxylic acid having 2 to 10 carbon atoms or its esters, preferably having 2 to 4 and more preferably having 2 to 3 carbon atoms ethylenically unsaturated carboxylic acid, most preferably acrylic acid, methacrylic acid or their esters, especially acrylic acid.
• the compounds of formula VII are present as a mixture of compounds described by this formula and by-products of the preparation process.
• compounds VII particular preference is given to the hydroxy group of up to six times, more preferably up to four times and very particularly preferably the tetra-ethoxylated compounds, referred to below as compounds VIIb. These have an increased hydrolytic stability.
• mixtures of the compounds VIIb and VIIc are advantageous, for example those having a weight ratio VIIb: VIIc of 10:90 to 90:10, preferably 20:80 to 80:20, particularly preferably 30:70 to 70:30 and very particularly preferably from 40:60 to 60:40.
• Equally preferred is one to 20 times, preferably one to ten times, more preferably two to ten times, very preferably two to five times, especially three to five times and especially three to four times alkoxylated, preferably ethoxylated, propoxylated or mixed-ethoxylated-propoxylated and particularly preferred ethoxylated glycerol (here exceptionally calculated in moles of alkoxy groups per mole of glycerol).
• the indicated degrees of alkoxylation in each case relate to the average degree of alkoxylation.
• the number average molecular weight M n of the alkoxylated polyols is preferably not more than 1000 g / mol, particularly preferably not more than 800 g / mol and very particularly preferably not more than 550 g / mol.
• the figures for the number-average and weight-average molecular weight M n and M w here relate to gel permeation chromatographic measurements using polystyrene as standard and tetrahydrofuran as eluent. The method is in the analyst paperback vol. 4, pages 433 to 442, Berlin 1984 described.
• Preferred alkoxylated sugar alcohols are those in which at least one hydroxy group of the sugar alcohol is not alkoxylated.
• the different alkoxy groups contained therein may be in a molar ratio of, for example, 0.05- 20: 1, preferably 0.1-10: 1 and more preferably 0.2-5: 1.
• polyhydric or polyhydric polyhydric alcohols are used in the esterification, it may be expedient for their use according to the invention as radical crosslinkers to partially esterify the polyhydric alcohols. This means that in an n-valent polyalcohol only at least 2 of the n-hydroxy groups are esterified with the carboxylic acid B.
• the stoichiometric excess of carboxylic acid B to be used is calculated to the desired degree of esterification, ie, for example, is 2 / n times the molar excesses indicated above.
• the esterification may also be, e.g. by cooling or dilution, are discontinued when the desired degree of esterification is reached.
• Ethylenically unsaturated carboxylic acids B which can be used according to the invention are those compounds which have at least one carboxyl group (-COOH), preferably one, and at least one, preferably one, ethylenically unsaturated group.
• the carboxylic acids which can be used according to the invention can be aliphatic, cycloaliphatic or aromatic, preferably aliphatic or cycloaliphatic and very particularly preferably aliphatic, straight-chain or branched and optionally substituted by functional groups.
• the carboxylic acids have from three to ten carbon atoms, preferably from three to five and more preferably from three to four.
• ethylenically unsaturated carboxylic acids B are acrylic acid, methacrylic acid, ethacrylic acid, maleic acid including its anhydride, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, vinylacetic acid, allylacetic acid or crotonic acid.
• Preferred carboxylic acids B are ⁇ , ⁇ - unsaturated carboxylic acids.
• methacrylic acid and acrylic acid in this document (meth) called acrylic acid, very particularly preferred is acrylic acid.
• Esterification catalysts C which can be used according to the invention are sulfuric acid, aryl or alkylsulfonic acids or mixtures thereof.
• arylsulfonic acids are benzenesulfonic acid, para-toluenesulfonic acid or dodecylbenzenesulfonic acid
• alkylsulfonic acids are methanesulfonic acid, ethanesulfonic acid or trifluoromethanesulfonic acid.
• Strongly acidic ion exchangers or zeolites can also be used as esterification catalysts. Preference is given to sulfuric acid and ion exchangers.
• Polymerization inhibitors D which can be used according to the invention are, for example, phenols, such as alkylphenols, for example o-, m- or p-cresol (methylphenol), 2-tert-butyl-4-methylphenol, 6-tert-butyl-2,4-dimethylphenol, 2,6-di-tert-butyl-4-methylphenol, 2-tert-butylphenol, 4-tert-butylphenol, 2,4-di-tert-butylphenol, 2-methyl-4-tert-butylphenol , 4-tert-butyl-2,6-dimethylphenol, or 2,2'-methylenebis (6-tert-butyl-4-methylphenol), 4,4'-oxydiphenyl, 3,4-methylenedioxydiphenol ( Sesamol), 3,4-dimethylphenol, hydroquinone, catechol (1,2-dihydroxybenzene), 2- (1'-methylcyclohex-1'-yl) -4,6-dimethylphenol, 2-
• hydroquinone monomethyl ether particularly preferred are hydroquinone monomethyl ether, hydroquinone, and alkylphenols, optionally in combination with Tripehnylphosphit and / or hypophosphorous acid.
• an oxygen-containing gas preferably air or a mixture of air and nitrogen (lean air) may be present.
• stabilizers preferred are those which are aerobic, i. those which require the presence of oxygen to develop their full inhibitory effect.
• Solvents E which can be used according to the invention are especially those which are suitable for the azeotropic removal of the water of reaction, if desired, in particular aliphatic, cycloaliphatic and aromatic hydrocarbons or mixtures thereof.
• n-pentane n-hexane, n-heptane, cyclohexane, methylcyclohexane, benzene, toluene or xylene.
• Particularly preferred are cyclohexane, methylcyclohexane and toluene.
• esterification can be carried out as follows:
• the esterification apparatus consists of a stirred reactor, preferably a reactor with circulation evaporator and an attached distillation unit with condenser and phase separation vessel.
• the reactor may be, for example, a reactor with double wall heating and / or internal heating coils.
• a reactor with external heat exchanger and natural or forced circulation i. using a pump, particularly preferably natural circulation, in which the circulation stream is accomplished without mechanical aids.
• reaction can also be carried out in several reaction zones, for example a reactor cascade of two to four, preferably two to three reactors.
• Suitable circulating evaporators are known in the art and described for example in R. Billet, Evaporation Technology, HTB-Verlag, bibliographisches Institut Mannheim, 1965, 53 , Examples of circulation evaporators are tube bundle heat exchangers, plate heat exchangers, etc.
• the distillation unit is of a type known per se. It may be a simple distillation, which is optionally equipped with a splash guard, or a rectification column. In principle, all conventional installations are suitable as column internals, for example trays, packings and / or fillings. Of the soils, bubble-cap trays, sieve trays, valve trays, Thormann trays and / or dual-flow trays are preferred; of the trays, those with rings, spirals, saddles or braids are preferred.
• the condenser and the separation vessel are of conventional design.
• Carboxylic acid B and polyhydric alcohol A are generally used in the esterification a) in a molar excess as stated above relative to the hydroxyl groups of the alcohol.
• the excess used can be up to about 1000: 1, if desired.
• esterification catalysts C As esterification catalysts C, the above-mentioned in question.
• They are generally used in an amount of from 0.1 to 5% by weight, based on the esterification mixture, preferably from 0.5 to 5, more preferably from 1 to 4 and very particularly preferably from 2 to 4% by weight.
• the esterification catalyst can be removed from the reaction mixture by means of an ion exchanger.
• the ion exchanger can be added directly to the reaction mixture and then filtered off or the reaction mixture can be passed through a Ionenor physicallyung.
• the esterification catalyst is left in the reaction mixture.
• the catalyst is an ion exchanger, it is preferably removed, for example by filtration.
• an oxygen-containing gas preferably air or a mixture of air and nitrogen (lean air) may be present.
• This oxygen-containing gas is preferably metered into the bottom region of a column and / or into a circulation evaporator and / or passed through the reaction mixture and / or via this.
• the polymerization inhibitor (mixture) D (as stated above) is used in a total amount of 0.01-1% by weight, based on the esterification mixture, preferably 0.02-0.8, particularly preferably 0.05-0.5,% by weight %.
• the above-mentioned compounds are suitable.
• the amount of solvent used is 10 to 200% by weight, preferably 20 to 100% by weight, particularly preferably 30 to 100% by weight, based on the sum of polyhydric alcohol and carboxylic acid B.
• the water contained in the reaction mixture is not removed via an azeotroping solvent, it is possible to remove it by stripping with an inert gas, preferably an oxygen-containing gas, more preferably air or lean air, for example as in US Pat DE-A 38 43 843 described.
• an inert gas preferably an oxygen-containing gas, more preferably air or lean air, for example as in US Pat DE-A 38 43 843 described.
• the reaction temperature of the esterification a) is generally 40-160 ° C, preferably 60-140 ° C and particularly preferably 80-120 ° C.
• the temperature can remain constant or increase in the course of the reaction, preferably it is raised in the course of the reaction.
• the final esterification temperature is 5 - 30 ° C higher as the initial temperature.
• the temperature of the esterification can be determined and controlled by varying the solvent concentration in the reaction mixture, as in DE-A 199 41 136 and the German application with the file number 100 63 175.4 described.
• a solvent If a solvent is used, it can be distilled off from the reaction mixture via the distillation unit attached to the reactor.
• the distillate may optionally be removed or, after condensation, passed into a phase separation apparatus.
• the aqueous phase thus obtained is usually discharged, the organic phase can be fed as reflux into the distillation unit and / or passed directly into the reaction zone and / or be passed into a circulation evaporator, as in German Patent Application No. 100 63 175.4 described.
• the organic phase As in the DE-A 199 41 136 described, used to control the temperature in the esterification.
• the esterification a) can be carried out without pressure but also at overpressure or underpressure, preferably working at normal pressure.
• the reaction time is usually 2 to 20 hours, preferably 4 to 15 and particularly preferably 7 to 12 hours.
• reaction components are not essential according to the invention. All components can be mixed and then heated or one or more components can not be initially or only partially charged and added after heating.
• the usable carboxylic acid B is not limited in its composition and in the case of crude (meth) acrylic acid, for example, the following components: (Meth) acrylic acid 90-99.9% by weight acetic acid 0.05-3% by weight propionic 0.01-1% by weight diacrylate 0.01-5% by weight water 0.05-5% by weight carbonyl 0.01-0.3% by weight inhibitors 0.01-0.1% by weight Maleic acid (anhydride) 0.001-0.5% by weight
• the crude (meth) acrylic acid used is generally stabilized with 200-600 ppm of phenothiazine or other stabilizers in amounts that allow comparable stabilization.
• carbonyl-containing for example, acetone and lower aldehydes, e.g. Formaldehyde, acetaldehyde, crotonaldehyde, acrolein, 2- and 3-furfural and benzaldehyde, understood.
• crude (meth) acrylic acid is meant here the (meth) acrylic acid-containing mixture obtained after absorption of the reaction gases of propane / propene / acrolein or isobutane / isobutene / methacrolein oxidation in an absorbent and subsequent separation of the absorbent or by fractionating Condensation of the reaction gases is obtained.
• pure (meth) acrylic acid can be used with, for example, the following purity: (Meth) acrylic acid 99.7 - 99.99% by weight acetic acid 50-1000 ppm by weight propionic 10 - 500 ppm by weight diacrylate 10 - 500 ppm by weight water 50-1000 ppm by weight carbonyl 1 - 500 ppm by weight inhibitors 1 - 300 ppm by weight Maleic acid (anhydride) 1 - 200 ppm by weight
• the pure (meth) acrylic acid used is generally stabilized with 100-300 ppm of hydroquinone monomethyl ether or other storage stabilizers in amounts which allow comparable stabilization.
• Purified or prepurified (meth) acrylic acid is generally understood to mean (meth) acrylic acid whose purity is at least 99.5% by weight and which is essentially free of the aldehydic, other carbonyl-containing and high-boiling components.
• an inert gas preferably an oxygen-containing gas, more preferably air or a mixture of air and nitrogen (lean air) may be circulated through or over the reaction mixture, for example in amounts of 0.1-1, preferably 0.2-0.8 and more preferably 0.3-0.7 m3 / m3h, based on the volume of the reaction mixture.
• the course of the esterification a) can be followed by monitoring the amount of water discharged and / or the decrease of the carboxylic acid concentration in the reactor.
• the reaction can be terminated, for example, as soon as 90% of the theoretically expected amount of water has been discharged through the solvent, preferably at least 95% and particularly preferably at least 98%.
• the end of the reaction can be determined, for example, by essentially removing no further water of reaction via the entraining agent. If carboxylic acid B is discharged together with the water of reaction, its proportion can be determined, for example, by back-titration of an aliquot of the aqueous phase.
• the reaction can be stopped with a suitable diluent G and reduced to a concentration of, for example, 10 to 90% by weight, preferably 20 to 80%, particularly preferably 20 to 60%, very particularly preferably 30 to 50% and in particular approx. 40% diluted, for example, to reduce the viscosity.
• the diluent G is selected from the group consisting of water, a mixture of water with one or more water-soluble organic solvents, or a mixture of water with one or more simple or polyfunctional alcohols, e.g. Methanol and glycerin.
• the alcohols preferably carry 1, 2 or 3 hydroxyl groups and preferably have from 1 to 10, in particular up to 4 carbon atoms. Preference is given to primary and secondary alcohols.
• the decolorization of the reaction mixture can be carried out at any point in the work-up procedure, for example at the stage of the crude reaction mixture or after any pre-wash, neutralization, washing or solvent removal.
• the reaction mixture may further be subjected to a pre-wash e) and / or a neutralization f) and / or a post-wash g), preferably only a neutralization f).
• neutralization f) and prewash e) can also be reversed in the order.
• carboxylic acid B for example (meth) acrylic acid and / or catalyst C can be at least partially recovered by acidification and extraction with a solvent and used again.
• the reaction mixture is in a washing machine with a washing liquid, for example water or a 5 to 30% by weight, preferably 5 to 20, particularly preferably 5 to 15% by weight sodium chloride, potassium chloride , Ammonium chloride, sodium sulfate or ammonium sulfate solution, preferably water or saline.
• a washing liquid for example water or a 5 to 30% by weight, preferably 5 to 20, particularly preferably 5 to 15% by weight sodium chloride, potassium chloride , Ammonium chloride, sodium sulfate or ammonium sulfate solution, preferably water or saline.
• the quantitative ratio of reaction mixture: washing liquid is generally 1: 0.1-1, preferably 1: 0.2-0.8, particularly preferably 1: 0.3-0.7.
• the laundry or neutralization may be carried out, for example, in a stirred tank or in other conventional equipment, e.g. in a column or mixer-settler apparatus.
• Sieve bottom or packed or packed columns, stirred tanks or mixer-settler apparatuses, as well as pulsed columns or those with rotating internals are preferably used.
• Prewash e is preferably used when metal salts, preferably copper or copper salts, are used as inhibitors (with).
• a post-wash g) may be advantageous for the removal of base or salt traces from the reaction mixture neutralized in f).
• the optionally prewashed reaction mixture which may still contain small amounts of catalyst and the majority of excess carboxylic acid, for example (meth) acrylic acid, having a 5-25, preferably 5-20, more preferably 5-15% by weight aqueous solution of a base, such as alkali or alkaline earth metal oxides, hydroxides, carbonates or bicarbonates, preferably sodium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate, potassium bicarbonate, calcium hydroxide, milk of lime, ammonia, ammonia or potassium carbonate, optionally 5 to 15% by weight of sodium chloride , Potassium chloride, ammonium chloride or ammonium sulfate may be added, particularly preferably with sodium hydroxide solution or sodium hydroxide solution, are neutralized.
• a base such as alkali or alkaline earth metal oxides, hydroxides, carbonates or bicarbonates, preferably sodium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate, potassium bicarbonate, calcium hydroxide
• the degree of neutralization is preferably 10 to 80 mol%, preferably 20 to 80 mol%, particularly preferably 40 to 80 mol%, based on the monomers containing acid groups. This neutralization can take place before and / or during the polymerization, preferably before the polymerization.
• the addition of the base takes place in such a way that the temperature in the apparatus does not rise above 60 ° C, preferably between 20 and 35 ° C and the pH is 4-13.
• the removal of the heat of neutralization is preferably carried out by cooling the container by means of internal cooling coils or via a double wall cooling.
• the quantitative ratio of reaction mixture: neutralizing liquid is generally 1: 0.1-1, preferably 1: 0.2-0.8, particularly preferably 1: 0.3-0.7.
• the reaction mixture is treated with such an amount of storage stabilizer, preferably hydroquinone monomethyl ether, that after removal of the solvent 100-500, preferably 200-500 and more preferably 200-400 ppm thereof are contained in the target ester (residue).
• storage stabilizer preferably hydroquinone monomethyl ether
• the distillative removal of the main amount of solvent is carried out, for example, in a stirred tank with double wall heating and / or internal heating coils under reduced pressure, for example at 20-700 mbar, preferably 30-500 and more preferably 50-150 mbar and a temperature of 40-80.degree ,
• the distillation can also take place in a falling film or thin film evaporator.
• the reaction mixture preferably several times in the circulation, under reduced pressure, for example at 20-700 mbar, preferably 30 to 500 and more preferably 50 to 150 mbar and a temperature of 40 to 80 ° C passed through the apparatus.
• an inert gas preferably an oxygen-containing gas, more preferably air or a mixture of air and nitrogen (lean air) can be introduced into the distillation apparatus, for example 0.1-1, preferably 0.2-0.8 and particularly preferably 0, 3 - 0.7 m3 / m3h, based on the volume of the reaction mixture.
• the residual solvent content in the residue after distillation is generally below 5% by weight, preferably 0.5-5% and particularly preferably 1 to 3% by weight.
• the separated solvent is condensed and preferably reused.
• solvent stripping i) may be carried out in addition to or instead of distillation.
• the target ester which still contains small amounts of solvent, heated to 50 - 90 ° C, preferably 80 - 90 ° C and removed the remaining amounts of solvent with a suitable gas in a suitable apparatus. If necessary, a vacuum can also be applied to assist.
• Suitable apparatuses are, for example, columns of a type known per se which contain the usual internals, e.g. Bodenv, beds or directed packings, preferably have beds.
• all standard installations are suitable as column internals, for example trays, packings and / or random packings.
• trays bell bottoms, sieve trays, valve trays, Thormann trays and / or dual-flow trays are preferred; of the trays are those with rings, coils, calipers, Raschig, Intos or Pall rings, Barrel or Intalox saddles, Top-Pak etc. or braids, preferred.
• a falling film, thin film or wiped film evaporator such as e.g. a Luwa, Rotafilm or Sambay evaporator, which can be equipped as a splash guard, for example, with a demister.
• Suitable gases are inert gases under the stripping conditions, preferably oxygen-containing gases, more preferably air or mixtures of air and nitrogen (lean air) or water vapor, in particular those which are heated to 50 to 100 ° C.
• the Strippgasmenge is for example 5 - 20, especially. preferably 10 to 20 and most preferably 10 to 15 m3 / m3h, based on the volume of the reaction mixture.
• the ester may be subjected to filtration j) to remove precipitated traces of salts and any decolorizing agent which may be present.
• the esterification a) of the polyhydric alcohol A with the carboxylic acid B is carried out in a molar excess of at least 5: 1 in the presence of at least one esterification catalyst C and at least one polymerization inhibitor D without a water azeotrope-forming solvent.
• the carboxylic acid B used in excess is essentially not separated in a preferred embodiment, ie only the proportion of carboxylic acid B is removed from the reaction mixture, which is determined by the volatility at the applied temperature and there are moreover no measures for the separation of the carboxylic acid such as, for example, distillative, rectificative, extractive, ie. washes, absorptive, such as passing over activated carbon or ion exchangers, and / or chemical steps, such as trapping the carboxylic acid with epoxides.
• the carboxylic acid B contained in the reaction mixture is preferably not more than 75% by weight, more preferably not more than 50% by weight, very preferably not more than 25% by weight, in particular not more than 10% by weight and especially not more separated from the reaction mixture as 5% by weight, based on the carboxylic acid B present in the reaction mixture after the end of the reaction.
• step b) can be dispensed with, so that only the proportion of water of reaction and carboxylic acid B is removed from the reaction mixture, which is determined by the volatility at the applied temperature. This can preferably be prevented by substantially complete condensation.
• esterification catalyst C used remains essentially in the reaction mixture.
• the reaction mixture thus obtained preferably has an acid number gem.
• a filtration step j) may be useful.
• the reaction mixture can be diluted in step c), in which case it is preferably reacted within 6 hours, more preferably within 3 hours to the hydrogel. Preferably, it can be neutralized in a step f).
• the mixture of substances may optionally be neutralized and have a pH, as listed above under f).
• Examples of (C 1 -C 4 ) -alkyl alcohol are methanol, ethanol, n-propanol or n-butanol.
• Particularly preferred hydrophilic monomers are acrylic acid and methacrylic acid.
• additional monoethylenically unsaturated compounds N which carry no acid groups, but are copolymerizable with the acid group-carrying monomers.
• these include, for example, the amides and nitriles of monoethylenically unsaturated carboxylic acid, eg. Acrylamide, methacrylamide and N-vinylformamide, N-vinylacetamide, N-methyl-vinylacetamide, acrylonitrile and methacrylonitrile.
• suitable compounds are, for example, vinyl esters of saturated C 1 - to C 4 -carboxylic acids such as vinyl formate, vinyl acetate or vinyl propionate, alkyl vinyl ethers having at least 2 C atoms in the alkyl group, such as.
• vinyl esters of saturated C 1 - to C 4 -carboxylic acids such as vinyl formate, vinyl acetate or vinyl propionate
• alkyl vinyl ethers having at least 2 C atoms in the alkyl group, such as.
• ethyl vinyl ether or butyl vinyl ether esters of monoethylenically unsaturated C 3 - to C 6 carboxylic acids, eg. B. esters of monohydric C 1 - to C 18 alcohols and acrylic acid, methacrylic acid or maleic acid, half esters of maleic acid, eg.
• Example maleic monoester, N-vinyl lactams such as N-vinylpyrrolidone or N-vinylcaprolactam, acrylic acid and methacrylic acid esters of alkoxylated monohydric, saturated alcohols, eg. Example, of alcohols having 10 to 25 carbon atoms, which have been reacted with 2 to 200 moles of ethylene oxide and / or propylene oxide per mole of alcohol, and monoacrylic and Monomethacrylklareester of polyethylene glycol or polypropylene glycol, wherein the molecular weights (M n ) of the polyalkylene glycols, for example bis to 2000 may be.
• Further suitable monomers are styrene and alkyl-substituted styrenes such as ethylstyrene or tert-butylstyrene.
• acid group-carrying monomers can also be used in mixture with other monomers, for. B. mixtures of vinyl acetate and 2-hydroxyethyl in any ratio. These are not acid group-carrying monomers the reaction mixture in amounts between 0 and 50 wt .-%, preferably less than 20 wt .-% added.
• the crosslinked (co) polymers consist of acid groups-carrying monoethylenically unsaturated monomers which are optionally converted before or after the polymerization in their alkali metal or ammonium salts, and from 0 to 40 wt .-% based on their total weight no acid group-carrying monoethylenically unsaturated monomers.
• hydrogels which are obtained by crosslinking polymerization or copolymerization of acid-group-carrying monoethylenically unsaturated monomers M or salts thereof.
• the starting polymer is treated with a postcrosslinker and preferably postcrosslinked during or after treatment by increasing the temperature and dried, the crosslinker preferably being contained in an inert solvent.
• inert solvents are meant those which essentially do not react with the starting polymer or with the postcrosslinker in the reaction. Preference is given to those solvents which do not react chemically with the starting polymer or postcrosslinker to more than 90%, preferably more than 95%, particularly preferably more than 99%, in particular more than 99.5%.
• Preference for postcrosslinking 1) and drying m) is in this case the temperature range between 30 and 250 ° C., in particular 50-200 ° C., very particularly preferably the range between 100 and 180 ° C.
• the application of the surface postcrosslinking solution is preferably carried out by spraying onto the polymer in suitable spray mixers. Following the spraying, the polymer powder is thermally dried, whereby the crosslinking reaction can take place both before and during drying.
• fluidized bed dryers can also be used.
• the drying can take place in the mixer itself, by heating the jacket or blowing hot air. Also suitable is a downstream dryer such as e.g. a rack dryer, a rotary kiln, or a heated screw. But it can also be e.g. an azeotropic distillation can be used as the drying process.
• the preferred residence time at this temperature in the reaction mixer or dryer is less than 60 minutes, more preferably less than 30 minutes.
• the starting polymer is a polymeric acrylic acid or a polyacrylate, in particular a polymeric acrylic acid or a polyacrylate, which have been obtained via radical polymerization and in which a polyfunctional ethylenically unsaturated radical crosslinker has been used.
• radical crosslinker is used in a dosage of from 0.01 to 5.0% by weight, preferably 0.02 to 3.0% by weight, very particularly preferably 0.03 to 2.5% by weight, in particular 0.05-1.0 and especially 0.1-0.75% by weight based on the starting polymer.
• the invention also relates to polymers prepared by one of the abovementioned processes and their use in hygiene articles, packaging materials and in nonwovens, and to the use of a mixture of substances mentioned above for the preparation of crosslinked or heat-crosslinkable polymers, in particular in paints and inks.
• hydrophilic, highly swellable hydrogels (starting polymers) to be used in this case are in particular polymers of (co) polymerized hydrophilic monomers M, graft (co) polymers of one or more hydrophilic monomers M onto a suitable graft base L, crosslinked cellulose or starch ethers or swellable in aqueous liquids Natural products, such as guar derivatives.
• These hydrogels are known to the person skilled in the art and are described, for example, in US Pat U.S. 4,286,082 . DE-C-27 06 135 . U.S. 4,340,706 . DE-C-37 13 601 . DE-C-28 40 010 . DE-A-43 44 548 .
• DE-A-40 20 780 EP-A-0 20 5674 .
• Suitable grafting bases L for hydrophilic hydrogels obtainable by graft copolymerization of olefinically unsaturated acids can be of natural or synthetic origin. Examples are starch, cellulose or cellulose derivatives and other polysaccharides and oligosaccharides, polyalkylene oxides, in particular polyethylene oxides and polypropylene oxides, and also hydrophilic polyesters.
• the water-absorbing polymer can be obtained via radical graft copolymerization of acrylic acid or acrylate onto a water-soluble polymer matrix.
• Suitable water-soluble polymer matrices include, but are not limited to, alginates, polyvinyl alcohol, and polysaccharides such as starch.
• a polyfunctional ethylenically unsaturated radical crosslinker is used.
• the water-absorbing polymer may be an organic-inorganic hybrid polymer of a polymeric acrylic acid or a polyacrylate on the one hand and a silicate, aluminate, or aluminosilicate on the other hand.
• a polymeric acrylic acid or polyacrylate obtained via free-radical polymerization in which a polyfunctional ethylenically unsaturated radical crosslinker was used and in the preparation of which a water-soluble silicate or soluble aluminate or mixtures of both were used.
• Preferred hydrogels are, in particular, polyacrylates, polymethacrylates and those disclosed in US Pat U.S. 4,931,497 .
• U.S. 5,011,892 and U.S. 5,041,496 described graft polymers.
• Very particularly preferred hydrogels are those in WO 01/38402 described kneader polymers and in DE 198 545 75 described hybrid organic-inorganic hydrogels based on polyacrylates.
• radical crosslinkers in hydrogels according to the invention can be used alone or in combination with other crosslinkers, for example internal or surface crosslinkers, for example the following:
• Suitable crosslinkers are in particular Methylenbisacryl- or - methacrylamide, esters of unsaturated mono- or polycarboxylic acids of polyols, such as diacrylate or triacrylate, z.
• polyols such as diacrylate or triacrylate
• allyl compounds such as allyl (meth) acrylate, triallyl cyanurate, Maleinklarediallylester, polyallylester, tetraallyloxyethane, triallylamine, tetraallylethylenediamine, allyl esters of phosphoric acid and vinylphosphonic, as described for example in EP-A-0 343 427 are described.
• hydrogels which are prepared using polyallyl ethers as crosslinkers and by acidic homopolymerization of acrylic acid are particularly preferred in the process according to the invention.
• Suitable crosslinkers are pentaerythritol tri- and tetraallyl ethers, polyethylene glycol diallyl ether, monoethylene glycol diallyl ether, glycerol di- and triallyl ethers, polyallyl ethers based on sorbitol, and ethoxylated variants thereof.
• crosslinkers are the polyethylene glycol diacrylates, ethoxylated derivatives of trimethylolpropane triacrylate, for example Sartomer SR 9035, and ethoxylated derivatives of glycerol diacrylate and glycerol triacrylate.
• polyethylene glycol diacrylates ethoxylated derivatives of trimethylolpropane triacrylate
• Sartomer SR 9035 ethoxylated derivatives of glycerol diacrylate and glycerol triacrylate.
• mixtures of the above crosslinkers can be used.
• the water-absorbing polymer is preferably a polymeric acrylic acid or a polyacrylate.
• the preparation of this water-absorbing polymer can be carried out by a method known from the literature. Preference is given to polymers which contain crosslinking comonomers (0.001-10 mol%), but very particular preference is given to polymers which have been obtained by free-radical polymerization and in which a polyfunctional ethylenically unsaturated radical crosslinker has been used.
• the hydrophilic, highly swellable hydrogels can be prepared by polymerization methods known per se.
• the polymerization in aqueous solution by the method of so-called gel polymerization.
• dilute, preferably aqueous, more preferably 15 to 50% by weight aqueous solutions of one or more hydrophilic monomers and optionally a suitable graft base L in are used Presence of a free-radical initiator preferably without mechanical mixing using the Trommsdorff-Norrish effect (Makromol Chem 1, 169 (1947)), polymerized.
• the polymerization reaction can be carried out in the temperature range between 0 ° C and 150 ° C, preferably between 10 ° C and 100 ° C, both at atmospheric pressure and under elevated or reduced pressure.
• the polymerization can also be carried out in a protective gas atmosphere, preferably under nitrogen.
• high-energy electromagnetic radiation or the usual chemical polymerization initiators K can be used, for.
• organic peroxides such as benzoyl peroxide, tert-butyl hydroperoxide, methyl ethyl ketone peroxide, cumene hydroperoxide, azo compounds such as azobisisobutyronitrile and inorganic peroxo compounds such as (NH 4 ) 2 S 2 O 8 , K 2 S 2 O 8 or H 2 O 2 .
• reducing agents such as ascorbic acid, sodium bisulfite, and iron (11) sulfate or redox systems containing as reducing component an aliphatic and aromatic sulfinic acid, such as benzenesulfinic acid and toluenesulfinic acid or derivatives of these acids, such as.
• reducing agents such as ascorbic acid, sodium bisulfite, and iron (11) sulfate or redox systems containing as reducing component an aliphatic and aromatic sulfinic acid, such as benzenesulfinic acid and toluenesulfinic acid or derivatives of these acids, such as.
• B. Mannich adducts of sulfinic acids, aldehydes and amino compounds, as described in the DE-C-1 301 566 described are used. After several hours of reheating the polymer gels in the temperature range 50 ° to 130 ° C, preferably 70 ° to 100 ° C, the quality properties of the polymers can
• the gels obtained are neutralized to 0-100 mol%, preferably to 25-100 mol%, and particularly preferably to 50-85 mol%, based on the monomer used, it being possible to use the customary neutralizing agents, preferably alkali metal hydroxides, alkali metal oxides or the corresponding alkali metal carbonates, but more preferably sodium hydroxide, sodium carbonate and sodium bicarbonate.
• the customary neutralizing agents preferably alkali metal hydroxides, alkali metal oxides or the corresponding alkali metal carbonates, but more preferably sodium hydroxide, sodium carbonate and sodium bicarbonate.
• the neutralization is achieved by mixing the neutralizing agent as an aqueous solution or preferably as a solid.
• the gel is mechanically comminuted, for example by means of a meat grinder, and the neutralizing agent is sprayed, sprinkled or poured over, and then thoroughly mixed.
• the gel mass obtained can be further gewolfft for homogenization.
• the neutralized gel mass is then dried with a belt or roller dryer until the residual moisture content is preferably below 10% by weight, in particular below 5% by weight.
• the polymerization per se can also be carried out by any other method described in the literature.
• the neutralization of the acrylic acid can also be carried out before the polymerization, as described above in step f).
• the polymerization can then be carried out continuously or else batchwise in a belt reactor known per se or in a kneading reactor.
• the initiation by means of electromagnetic radiation preferably by means of UV radiation, or alternatively the initiation with a redox initiator system is particularly preferred.
• the dried hydrogel can then be ground and sieved, with mill mills usually being equipped with roller mills, pin mills or vibratory mills.
• the preferred particle size of the sieved hydrogel is preferably in the range 45-1000 ⁇ m, preferably 45-850 ⁇ m, more preferably 200-850 ⁇ m, and most preferably 300-850 ⁇ m. In these ranges are preferably 80 wt .-% of the particles, in particular 90 wt .-% of the particles.
• the size distribution can be determined with established laser methods.
• the present invention furthermore relates to crosslinked hydrogels which contain at least one hydrophilic monomer M in copolymerized form and are crosslinked with an ester F of a polyhydric alcohol A with at least one ethylenically unsaturated carboxylic acid B.
• the ester can be prepared according to the invention or in a manner known in the art are prepared, preferably in the inventive manner.
• ester F such compounds can be used as described above.
• Polyalcohols A and ethylenically unsaturated carboxylic acids B are also those as described above.
• esters in which the polyhydric alcohol A is selected from the list of polyol which has at least one ether, carboxyl or C 1 -C 4 -alkyloxycarbonyl function as additional functionality, sugar alcohols, partially alkoxylated sugar alcohols, polyesterols, at least partially alkoxylated polyesterols and at least partially saponified, alkoxylated polyesterols, as described above in each case.
• esters F in which the polyhydric alcohol A is selected from the list of ditrimethylolpropane, dipentaerythritol, dimethylolpropionic acid and dimethylolbutyric acid.
• the polyalcohols A in esters F described by formula VII which are used as crosslinking agents in the abovementioned hydrogels, can each be ethoxylated, propoxylated or mixed ethoxylated and propoxylated and in particular exclusively ethoxylated, ie R 10 in formula VII can, for example, independently of one another Hydrogen and / or methyl and especially exclusively hydrogen.
• esters F of the formula VII are those esters F of a polyhydric alcohol A containing at least one ethylenically unsaturated carboxylic acid B, where the polyhydric alcohol A is glycerol three to four times ethoxylated per glycerol or trimethylolpropane or pentaerythritol quadruply ethoxylated per hydroxyl group ,
• the CRC value [g / g] of the hydrogel-forming polymers according to the invention can be measured by the methods given in the description and is preferably greater than 15, in particular 16, 18, 20, 22, 24 or higher, particularly preferably 25 at 26, 27, 28, 29, more preferably at 30, 31, 32, 33, 34, 35, 36, 37 or higher.
• the AUL 0.7 psi value [g / g] of the hydrogel-forming polymers according to the invention can be measured by the methods given in the description and is preferably greater than 8, in particular 9, 10, 11, 12, 13, 14 or higher, particularly preferred at 15 in particular at 16, 17, 18, 19, or higher, especially preferably greater than 20, in particular 21, 22, 23, 24, 25, 26, 27, 28, or higher.
• the AUL 0.5 psi value [g / g] of the hydrogel-forming polymers according to the invention can be measured by the methods given in the description and is preferably greater than 8, in particular 9, 10, 11, 12, 13, 14 or higher, particularly preferably at 15, in particular at 16, 17, 18, 19, or higher, particularly preferably greater than 20, in particular 21, 22, 23, 24, 25, 26, 27, 28, or higher.
• the percentages are to be understood as meaning that at 10-100% by weight, 11, 12, 13, 14, 15, 16, 17, 18, 19 up to 100% by weight of hydrogel-forming polymer according to the invention and all intervening% -Inve (eg 12.2%) are possible and corresponding hydrophilic fiber material from 0 to 89, 88, 87, 86, 85, 83, 82, 81 wt .-% and intervening percentages (eg 87.8%) possible are. If there are other materials in the core, the percentage of polymer and fiber decreases accordingly.
• the analogue applies to the preferred ranges, e.g.
• hydrogel-forming polymer according to the invention in the preferred range 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 to 100% by weight of hydrogel-forming polymer according to the invention, in the more preferred range 30, 31, 32, 33, 34, 35, 36, 37, 38, 39 to 100% by weight of hydrogel-forming polymer according to the invention, more preferably 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 to 100% by weight.
• % of hydrogel-forming polymer according to the invention in the more preferred range 50, 51, 52, 53, 54, 55, 56, 57, 58, 59 to 100% by weight of hydrogel-forming polymer according to the invention, in the particularly preferred range 60, 61, 62, 63, 64, 65, 66, 67, 68, 69 to 100% by weight of hydrogel-forming polymer according to the invention, in the especially preferred range 70, 71, 71, 72, 73, 74, 75, 76, 77, 78 , 79 to 100% by weight of hydrogel-forming polymer according to the invention and in the most preferred range 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 or 100% by weight of hydrogel-forming polymer according to the invention ,
• Hygiene articles include incontinence pads and incontinence pants for adults as well as diapers for babies.
• the liquid pervious cover (P) is the layer that has direct skin contact.
• the material for this consists of conventional synthetic or semi-synthetic fibers or films of polyester, polyolefins, rayon or natural fibers such as cotton.
• the fibers are usually to be connected by binders such as polyacrylates.
• Preferred materials are polyester, rayon and their blends, polyethylene and polypropylene. Examples of liquid-permeable layers are described in WO 99/57355 A1 . EP 102 388 3 A2 ,
• the liquid-impermeable layer (Q) is usually made of a film of polyethylene or polypropylene.
• the core (R) contains hydrophilic fiber material in addition to the hydrogel-forming polymer according to the invention.
• Hydrophilic is understood to mean that aqueous liquids spread quickly over the fiber.
• the fibrous material is cellulose, modified cellulose, rayon, polyesters such as polyethylene terephthalate. Particularly preferred are cellulose fibers such as pulp.
• the fibers generally have a diameter of 1 to 200 .mu.m, preferably 10 to 100 .mu.m. In addition, the fibers have a minimum length of 1 mm.
• diapers The structure and shape of diapers is well known and, for example, in WO 95/26 209 p. 66 line 34 to p. 69 line 11, DE 196 04 601 A1 . EP-A-0 316 518 and EP-A-0 202 127 described. Generally, diapers and other toiletries are also in WO 00/65084 especially on pages 6-15, WO 00/65348 especially on pages 4 - 17, WO 00/35502 , especially pages 3-9, DE 19737434 . WO 98/8439 described. Hygiene articles for feminine hygiene are described in the following references. The aqueous fluids absorbent hydrogel-forming polymers according to the invention can be used there.
• Literature Feminine Hygiene WO 95/24173 : Absorption Article for Controlling Odor, WO 91/11977 : Body Fluid Odor Control, EP 389023 : Absorbent Sanitary Articles, WO 94/25077 : Odor Control Material, WO 97/01317 : Absorbent Hygienic Article, WO 99/18905 . EP 834297 . US 5,762,644 . US 5,895,381 . WO 98/57609 . WO 2000/065083 . WO 2000/069485 . WO 2000/069484 . WO 2000/069481 . US 6,123,693 . EP 1104666 . WO 2001/024755 .
• WO 2001/24729 Incontinence articles are described in the following documents: Disposable Absorbent Article for Incontinent Individuals: EP 311344 Description pp. 3 - 9; Disposable Absorbent Article: EP 850623 ; Absorbent Article: WO 95/26207 ; Absorbent Article: EP 894502 ; Dry Laid Fibrous Structure: EP 850 616 ; WO 98/22063 ; WO 97/49365 ; EP 903134 ; EP 887060 ; EP 887059 ; EP 887058 ; EP 887057 ; EP 887056 ; EP 931530 ; WO 99/25284 ; WO 98/48753 , Feminine hygiene and incontinence products are described in the following documents: Catamenial Device: WO 93/22998 Description pp.
• hydrogel-forming polymers according to the invention are outstandingly suitable as absorbents for water and aqueous liquids, so that they can be used advantageously as a water-retaining agent in agricultural horticulture, as a filtration aid and especially as an absorbent component in hygiene articles such as diapers, tampons or sanitary napkins.
• the absorbent composition of the present invention has compositions containing or fixed to the high swellable hydrogels.
• Any composition is suitable that can accommodate the high swellable hydrogels and which can also be integrated into the absorption layer.
• a variety of such compositions are already known and described in detail in the literature.
• a composition for incorporation of highly swellable hydrogels may, for. Example, a fiber matrix, which consists of a cellulose fiber mixture (air-laid web, wet laid web) or of synthetic polymer fibers (meltblown web, spunbonded web), or from a mixed fiber plant of cellulose fibers and synthetic fibers. Possible fiber materials are described in detail in the following chapter. For example, the process of an air-laid web is described in WO 98/28 478 , Furthermore, open-cell foams or the like can serve for the incorporation of high-swellable hydrogels.
• such a composition may be formed by fusing two monolayers to form one or more of a plurality of chambers containing the high swellable hydrogels.
• a chamber system is described in detail in EP 0 615 736 A1 P. 7 line 26 ff.
• At least one of the two layers should be water permeable.
• the second layer can either be water-permeable or impermeable to water.
• Tissues or other fabric, closed or open-cell foams, perforated films, elastomers or fabrics of fibrous material can be used as the layer material.
• the layer material should have a pore structure whose pore dimensions are small enough to retain the high swellable hydrogel particles.
• the above examples of composition of the absorbent composition also include laminates of at least two layers, between which the high swellable hydrogels are incorporated and fixed.
• Dry and wet Integrity is the ability to incorporate highly swellable hydrogels into the absorbent composition so that they will withstand external forces in both the wet and dry states and will not displace or leak high swellable polymer. Force effects are to be understood primarily as mechanical loads, as they occur in the course of movement when the hygiene article is worn, or else the weight load under which the hygiene article stands, especially in the case of incontinence.
• fixation by heat treatment addition of adhesives, thermoplastics, binder materials are listed in WO 95/26209 P. 37 line 36 to p. 41 line 14. Said passage is thus part of this invention. Methods for increasing the wet strength can also be found in WO 2000/36216 A1 ,
• the absorbent composition of a carrier material such as Example, consist of a polymer film on which the sharkquellschreiben hydrogel particles are fixed. The fixation can be made both on one side and on both sides.
• the carrier material may be water-permeable or impermeable to water.
• compositions of the absorbent composition are the high swellable hydrogels in a weight fraction of 10 to 100 wt%, preferably 20 to 100 wt .-%, more preferably 30 to 100 wt .-%, even more preferably 40 to 100 wt .-%, more preferably 50-100% by weight, more preferably 60-100% by weight, especially preferably 70-100% by weight, most preferably 80-100% by weight and most preferably 90-100% by weight based on the Total weight of the composition and the highly swellable hydrogels installed.
• Fiber materials of the absorbent composition are Fiber materials of the absorbent composition
• the structure of the present absorbent composition according to the invention is based on a variety of fiber materials which are used as a fiber network or matrices. Included in the present invention are both fibers of natural origin (modified or unmodified) and synthetic fibers.
• cellulosic fibers include those commonly used in absorbent products, such as fluff pulp and cotton type pulp.
• the materials (coniferous or hardwoods), production methods such as chemical pulp, semi-chemical pulp, chemothermic mechanical pulp (CTMP) and bleaching method are not particularly limited.
• CMP chemothermic mechanical pulp
• natural cellulose fibers such as cotton, flax, silk, wool, jute, ethyl cellulose and cellulose acetate are used.
• Suitable synthetic fibers are made from polyvinyl chloride, polyvinyl fluoride, polytetrafluoroethylene, polyvinylidene chloride, polyacrylics such as ORLON ®, polyvinyl acetate, polyethylvinyl acetate, polyvinyl alcohol soluble or insoluble.
• thermoplastic polyolefin such as polyethylene fibers (PULPEX ®), polypropylene fibers and polyethylene-polypropylene bicomponent fibers
• polyester fibers such as polyethylene terephthalate (DACRON ® or KO-DEL ®), copolyesters, polyvinyl acetate, polyethylvinyl acetate, polyvinyl chloride, polyvinylidene chloride, polyacrylics, polyamides , Copolyamides, polystyrene and copolymers of the above-mentioned polymers, and polyethylene terephthalate polyethylene-isophthalate copolymer bicomponent fibers, polyethylvinyl acetate / polypropylene, polyethylene / polyester, polypropylene / polyester, copolyester / polyester, polyamide fibers (nylon), polyurethane fibers, polystyrene fibers, and polyacrylonitrile fibers.
• thermoset two-component fibers of sheath-core-type polyolefin and side-by-side type because of their excellent dimensional stability after liquid absorption.
• thermoplastic fibers are preferably used in combination with thermoplastic fibers.
• thermoplastic fibers During the heat treatment, the latter partly migrate into the matrix of the existing fiber material and thus form connecting points and renewed stiffening elements on cooling.
• thermoplastic fibers means an extension of the pore dimensions present after heat treatment. In this way it is possible, by continuously adding thermoplastic fibers during the formation of the absorption layer, to continuously increase the proportion of thermoplastic fibers to the cover sheet, resulting in a likewise continuous increase in pore sizes.
• Thermoplastic fibers can be formed from a variety of thermoplastic polymers having a melting point of less than 190 ° C, preferably between 75 ° C and 175 ° C. At these temperatures, no damage to the cellulose fibers is to be expected.
• Lengths and diameters of the above-described synthetic fibers are not particularly limited, and generally, any fiber having a length of 1 to 200 mm and a diameter of 0.1 to 100 denier (gram per 9000 meters) may be preferably used.
• Preferred thermoplastic fibers have a length of 3 to 50 mm, more preferably a length of 6 to 12 mm.
• the preferred diameter of the thermoplastic fiber is between 1.4 and 10 decitex, more preferably between 1.7 and 3.3 decitex (grams per 10,000 meters).
• the shape is not particularly limited, and examples include cloth-like, narrow cylinder-like, cut / split-yarn-type, staple-type and endless-fiber-like ones.
• the fibers in the absorbent composition of the invention may be hydrophilic, hydrophobic or a combination of both.
• a fiber is said to be hydrophilic if the contact angle between the liquid and the fiber (or its surface) is less than 90, or if the liquid tends to spontaneously spread on the same surface. Both processes are usually coexistent.
• a fiber is said to be hydrophobic if a contact angle of greater than 90 ° is formed and no spreading is observed. Preference is given to using hydrophilic fiber material.
• Fiber material is particularly preferably used which is weakly hydrophilic toward the body side and most hydrophilic in the region around the highly swellable hydrogels.
• the use of layers of different hydrophilicity produces a gradient which channels the impinging liquid to the hydrogel, where finally the absorption takes place.
• Suitable hydrophilic fibers for use in the absorbent composition according to the invention are, for example, cellulose fibers, modified cellulose fibers, rayon, polyester fibers, such as e.g. As polyethylene terephthalate (DACRON ®), and hydrophilic nylon (HYDROFIL ®).
• Suitable hydrophilic fibers can also be obtained by hydrophilizing hydrophobic fibers, such as the treatment of thermoplastic fibers obtained from polyolefins (such as polyethylene or polypropylene, polyamides, polystyrenes, polyurethanes, etc.) with surfactants or silica.
• polyolefins such as polyethylene or polypropylene, polyamides, polystyrenes, polyurethanes, etc.
• surfactants or silica for reasons of cost and availability, however, cellulose fibers are preferred.
• the highly swellable hydrogel particles are embedded in the described fiber material. This can be done in many ways by z. B. with the hydrogel material and the fibers together builds up an absorption layer in the form of a matrix, or by incorporation harnesslCher hydrogels in layers of fiber mixture, where they are finally fixed, either by adhesive or lamination of the layers.
• the liquid-receiving and -istrating fiber matrix may consist of synthetic fiber or cellulose fiber or a mixture of synthetic fiber and cellulose fiber, wherein the mixing ratio of (100 to 0) synthetic fiber: (0 to 100) cellulose fiber may vary.
• the cellulose fibers used can additionally be chemically stiffened to increase the dimensional stability of the hygiene article.
• a fiber stiffening can be achieved by adding suitable coatings to the fiber material.
• suitable coatings include, for example, polyamide-epichlorohydrin coatings (Kymene ® 557 H, Hercoles, Inc. Wilmington, Delaware, USA), polyacrylamide coatings (as described in U.S. Patent 3,556,932 or as a commercial product from Parez ® 631 NC trademark, American Cyanamid Co., Stamford, CT, USA), melamine-formaldehyde coatings and polyethyleneimine coatings with one.
• the chemical stiffening of cellulose fibers can also be done by chemical reaction. So z.
• suitable crosslinker substances can cause crosslinking that occurs within the fiber.
• Suitable crosslinker substances are typical substances which are used for crosslinking monomers. Included, but not limited to, are C 2 -C 8 dialdehydes, C 2 -C B monoaldehydes with acidic functionality, and especially C 2 -C 9 polycarboxylic acids. Specific substances from this series are, for example, glutaraldehyde, glyoxal, glyoxylic acid, formaldehyde and citric acid.
• Chemically crosslinked cellulose fibers are known and known in WO 91/11162 .
• the chemical crosslinking causes a stiffening of the fiber material, which is ultimately reflected in an improved dimensional stability of the entire hygiene article.
• the individual layers are known by those skilled methods, such.
• the absorbent composition is comprised of compositions containing high swellable hydrogels and the high swellable hydrogels that are present in or attached to said compositions.
• Examples of methods of obtaining an absorbent composition consisting of, for example, a support material to which one or both sides highly swellable hydrogels are fixed are known and included in, but not limited to, the invention.
• Examples of methods of obtaining an absorbent composition consisting of, for example, highly swellable hydrogels (c) embedded in a fiber material mixture of synthetic fibers (a) and cellulose fibers (b), wherein the mixing ratio of (100 to 0) is synthetic fiber : (0 to 100) cellulose fiber can vary, (1) a process in which (a), (b) and (c) are mixed simultaneously, (2) a process in which a mixture of (a) and ( b) in (c), (3) a process in which a mixture of (b) and (c) is mixed with (a), (4) a process in which a mixture of (a) and ( c) in (b), (5) a process in which (b) and (c) are mixed and (a) continuously metered in, (6) a process in which (a) and (c) are mixed and (b) is metered in continuously, and (7) a method in which (b) and (c) are separately mixed in (a).
• methods (1) and (5) are preferred.
• the suitably produced absorbent composition may optionally be subjected to a heat treatment so as to result in an absorbent layer excellent in wet-state dimensional stability.
• the method of heat treatment is not particularly limited. Examples include heat treatment by supplying hot air or infrared radiation.
• the temperature in the heat treatment is in the range 60 ° C to 230 ° C, preferably between 100 ° C and 200 ° C, more preferably between 100 ° C and 180 ° C.
• the duration of the heat treatment depends on the type of synthetic fiber, its quantity and the speed of production of the hygiene article. Generally, the duration of the heat treatment is between 0.5 second to 3 minutes, preferably 1 second to 1 minute.
• the absorbent composition is generally provided, for example, with a liquid permeable cover layer and a liquid impermeable backsheet. Wieterhin leg cuffs and adhesive tapes are attached and finished so the toiletries.
• the materials and types of the permeable topsheet and impermeable backsheet, as well as the leg seals and tapes are well known to those skilled in the art and not particularly limited. Examples of this can be found in WO 95/26209 ,
• esters F which can be used as crosslinkers do not have to be purified after their preparation, especially that the carboxylic acid B, for example acrylic acid, does not have to be separated off, since this usually constitutes a monomer for preparing the hydrogels.
• the production of the superabsorbent crosslinking agents takes place in the examples by esterification of polyetherols with acrylic acid, wherein the separation of the water takes place in an azeotropic distillation.
• Esterification catalyst is sulfuric acid in the examples.
• the reactants are presented together with a stabilizer mixture consisting of hydroquinone monomethyl ether, triphenyl phosphite and hypophosphorous acid in the examples in methylcyclohexane as entraining agent.
• the reaction mixture is then heated to about 98 ° C until the azeotropic distillation begins. During azeotropic distillation, the temperature in the reaction mixture increases. The amount of water removed is determined. The distillation is stopped when at least the theoretical amount of water has been separated off. Subsequently, the entrainer is removed in a vacuum distillation.
• the product is cooled and used as a crosslinker in superabsorbent production.
• Example 7 (about 3 times per glycerol molecule ethoxylated glycerol triacrylate)
• Example 8 (about 5 times per glycerol molecule ethoxylated glycerol triacrylate)
• Example 9 (about 9 times per glycerol molecule ethoxylated glycerol triacrylate)
• Example 10 (about 5 times per molecule of pentaerythritol ethoxylated pentaerytritol tetraacrylate)
• 382 parts of approximately 5-fold ethoxylated pentaerythritol are esterified with 348 parts of acrylic acid and 5 parts of sulfuric acid in 180 parts of methylcyclohexane.
• As auxiliaries 3 parts of hydroquinone monomethyl ether, 1.5 parts of triphenyl phosphite and 1.5 Part of hypophosphorous acid added.
• the product is cleaned via K300 filter.
• the acid number is 35 mg KOH / g.
• the viscosity of the dark colored product is 280 mPas.
• Example 11 (approximately 13 times per molecule of ethoxylated dipentaerythritol)
• Example 12 (about 4 times per molecule of ethoxylated sorbitol acrylate)
• Example 13 (about 6 times per molecule of ethoxylated sorbitol acrylate)
• 601 parts of approximately 6-fold ethoxylated sorbitol are esterified with 444 parts of acrylic acid and 5 parts of sulfuric acid in 448 parts of cyclohexane.
• As auxiliaries 3 parts of hydroquinone monomethyl ether, 1.5 parts of triphenyl phosphite and 1.5 parts of hypophosphorous acid are added.
• the acid number is 45 mg KOH / g.
• the viscosity of the dark colored product is 700 mPas.
• Example 14 (about 8 times per molecule of ethoxylated sorbitol acrylate)
• Example 15 (about 10 times per molecule of ethoxylated sorbitol acrylate)
• Example 16 (about 13 times per molecule of ethoxylated sorbitol hexaacrylate)
• the dried hydrogel can be investigated by the following test methods.
• the free swellability of the hydrogel is determined in a tea bag.
• a tea bag For the determination of the CRC, 0.2000 ⁇ 0.0050 g of dried hydrogel (particle fraction 106-850 ⁇ m) are weighed into a 60 ⁇ 85 mm tea bag, which is subsequently welded. The teabag is placed in an excess of 0.9% by weight saline for 30 minutes (at least 0.83 liter of saline solution / 1 g of polymer powder). The teabag is then centrifuged for 3 minutes at 250 g. The determination of the amount of liquid is done by weighing the centrifuged teabag.
• the measuring cell for the determination of the AUL 0.7 psi represents a Plexiglas cylinder with an inner diameter of 60 mm and a height of 50 mm, which has on the underside a glued stainless steel sieve bottom with a mesh size of 36 ⁇ m.
• the measuring cell also includes a plastic plate with a diameter of 59 mm and a weight, which can be placed together with the plastic plate in the measuring cell. The weight of the plastic plate and the weight together amount to 1345g.
• the weight of the empty Plexiglas cylinder and the plastic plate is determined and recorded as Where.
• a round filter paper with a diameter of 90 mm and a pore size ⁇ 20 ⁇ m (S & S 589 Schwarzband from Schleicher & Schüll) is placed on the ceramic plate.
• the hydrogel-forming polymer-containing Plexiglas cylinder is now placed with plastic plate and weight on the filter paper and left there for 60 minutes. After this time, remove the complete unit from the Petri dish from the filter paper and then remove the weight from the Plexiglas cylinder.
• the swollen hydrogel Plexiglas cylinder is weighed together with the plastic plate and the weight recorded as W b.
• crosslinkers the types indicated in Table 1 were added in the amounts indicated there, in each case based on acrylic acid used. Thereafter, 0.28% by weight of sodium persulfate and 0.0056% by weight of ascorbic acid, based in each case on the acrylic acid monomer used, were added as the polymerization initiator.
• the reaction started, and the temperature of the kneader shell was readjusted so that the heat of reaction was not dissipated through the jacket. This results in an almost adiabatic heating of the reaction mixture, where the polymerization takes place with stirring. At the end of the reaction, the temperature is maintained for about an hour. Afterwards, a fine-crumb gel was emptied.
• the gel was dried for 3 h at 160 C in a convection oven, ground with a laboratory roller mill, and sieved at 100-850 microns. This is the normal base polymer of Table 1.
• the gel was first annealed for 6 hours at 90 ° C. in the sealed plastic bag, and only then was it dried for 3 hours at 160 ° C. in a circulating air oven, ground with a laboratory roller mill, and finally screened at 100-850 microns.
• This is the hydrolyzed base polymer of Table 1.
• the dry normal base polymer powder was combined with a solution of 0.06 wt.% Ethylene glycol diglycidyl ether (Nagase, Japan), 3.43 wt.% Water and 1.47 wt.% Propane-1,2-diol, based on the polymer used Stirring homogeneously sprayed.
• the wet powder was then tempered in the oven at 150 C for 60 min. It was then sieved again at 850 microns to remove agglomerates.
• Table 1 example crosslinkers amount used solubility base polymer Postcrosslinked polymer CRC Extract. 16h CRC AUL 0.7 psi Extract.

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